Circuit switching and packet switching are different and well-known methods for establishing a connection between two endpoints to permit the exchange of voice or data signals. In the dial-up telephone network, for example, a caller's line goes to a switching center or switch, where the actual connection is made to the called party. In the case of a circuit switch, a permanent connection is set-up and maintained for the duration of the call. A packet switch does not establish a permanent connection, rather the information is assembled in packets that are transmitted rapidly over a channel dedicated to the connection only for the duration of the packet's transmission.
Telephone systems based on IP packet switching offer many advantages over circuit switching systems. In particular, packet switching telephone systems have a distributed architecture and offer a wide variety of features that are difficult or costly to implement in circuit switched telephone systems and the separation of telephony services from telephony access allows their independent evolution. Moreover, adapting multiple PBXs to a single network telephony server (and hence a single distributed PBX) represents a significant consolidation opportunity (of a multi node network into a large single node network) and hence a simplification value-add.
Most PBX systems in existence today are circuit switched devices. In order to offer the above advantages to customers who own these existing PBXs, telephone equipment manufacturers are developing and commercializing packet switched telephone systems that are intended to replace existing PBX devices, or they are evolving their legacy TDM PBXs. This latter method may be preferred by customers who are hesitant to replace their existing PBX when it is not yet totally obsolete.
Accordingly, there is a need in the industry to develop a novel approach to upgrade a PBX such that it can benefit from this new packet switched telephony systems paradigm.